Popular smoking articles, such as cigarettes, have a substantially rod shaped structure and include a charge of smokable material such as strands or shreds of tobacco (e.g., cut filler) surrounded by a paper wrapper thereby providing a so-called "tobacco rod." Numerous popular cigarettes have cylindrical filter elements aligned in an end-to-end relationship with the tobacco rod. Typically, filter elements are constructed from fibrous materials such as cellulose acetate, have a circumscribing plug wrap, and are attached to the tobacco rod using tipping material.
Many types of smoking products and improved smoking articles have been proposed through the years as improvements upon, or as alternatives to, the popular smoking articles. Recently, U.S. Pat. Nos. 4,708,151 to Shelar; 4,714,082 to Banerjee et al.; 4,756,318 to Clearman et al.; and 4,793,365 to Sensabaugh, Jr. et al.; and European Patent Publication Nos. 212,234 and 277,519 propose cigarettes and pipes which comprise a fuel element, an aerosol generating means physically separate from the fuel element, and a separate mouth-end piece. Such types of smoking articles provide natural tobacco flavors to the smoker thereof by heating, rather than burning, tobacco in various forms.
Flavor and aroma are important characteristics of smoking articles. To improve the flavor and aroma in smoking articles, flavorful and aromatic substances, including various natural extracts, have been included in smoking articles. For example, various processes for producing and using tobacco extracts, aroma oils and concentrates are proposed in the U.S. Patent Nos. 3,136,321 to Davis; 3,316,919 to Green; 3,424,171 to Rooker; 4,421,126 to Gellatly and 4,506,682 to Mueller and European Patent Publication No. 338,831 to Clapp et al.
In addition, it is known that tobacco flavorants can be generated by Maillard Reactions or "browning reactions" in which an amino acid reacts with a sugar at elevated temperature. Two possible pathways for Maillard Reactions have been proposed. In the first, sugar molecules react with amino acids to form Amadori or Heyns products, which then undergo a series of rearrangement to form alkylpyrazines. In the second proposed pathway, sugars initially undergo degradation and rearrangements to form smaller carbonyl compounds which then condense with nitrogen from amino acids to form alkylpyrazine compounds. See Koehler et al., J. Agr. Food Chem., 18(5):895-898 (1970).
U.S. Pat. No. 3,920,026 discloses using synthetically prepared Maillard Reaction products as tobacco flavorants. These products are prepared by Maillard Reactions, i.e., by reacting one or more amino acids, preferably valine, with a sugar or a carbonyl compound that functions as a sugar substitute in the Maillard Reaction. The carbonyl compound that functions as a sugar substitute in the Maillard Reaction can be dihydroxyacetone or pyruvaldehyde.
U.S. Pat. No. 3,722,516 to Suwa describes a tobacco product having added thereto the Maillard-functional sugar substitute, dihydroxyacetone. The added dihydroxyacetone is said to react with the amino acids and ingredients analogous thereto present in the tobacco materials, thereby improving the desirable natural flavor characteristics of the tobacco materials. Dihydroxyacetone is added in an amount between 0.01 weight percent and 1.0 weight percent, based on the weight of the tobacco materials. Exogenous amino acids can also be added with dihydroxyacetone in an amount which is approximately the same as or less than the amount of dihydroxyacetone. Such amino acids include arginine, leucine, valine, lysine, asparagine, threonine, proline, phenylalanine, glycine, glutamine and ornithine.
U.S. Pat. No. 5,413,122 to Shu issued on May 9, 1995 discloses making a flavorful and aromatic composition from .beta.-hydroxy .alpha.-amino acids by mixing the amino acids with a liquid having an aqueous character followed by heat treatment in an enclosed environment to provide an aqueous solution of volatile pyrazine flavorants. The ratio of liquid to amino acid is 4:1 to 40:1. The resulting aqueous extract containing flavorful pyrazines is then applied to smoking materials to provide flavor and aroma in the smoking articles.
Because of the volatile nature of flavorant and aroma materials, the compositions can be lost in part or entirely during manufacturing steps subsequent to application of the materials to tobacco. Also quantities of the flavorant and aroma materials can diminish during the storage of the finished smoking article and it is often necessary to increase the initial content of flavorants to compensate.